# The number of toy kangaroos, K, in a toy box after 't' days is given by #K=t^2+20t#. Estimate the rate at which the number of kangaroos is changing after 3 days?

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#K=t^2+20t#

##### 1 Answer

Apr 13, 2018

#### Answer:

After 3 days, the number of kangaroos is increasing by 26 kangaroos per day.

#### Explanation:

The rate of change of a function is the derivative of that function.

First take the derivative of

The derivative of

So the derivative of

The derivative of

You should end up with

The question wants to know the rate of change after 3 days, so just plug in 3:

So there you have it- after 3 days, the number of kangaroos is increasing by 26 kangaroos per day.